As one aspect of an underpants-type disposable diaper, there has been known an underpants-type disposable diaper including an outer body formed in a cylindrical shape by joining both side portions of a ventral side outer body and both side portions of a dorsal side outer body and an inner body that is provided from a central portion of an inner surface of the ventral side outer body in a width direction to a central portion of an inner surface of the dorsal side outer body in a width direction, and absorbs excretion, wherein the ventral side outer body and the dorsal side outer body are not continuous but separated from each other on the crotch side (refer to Patent Documents 1 to 4). Such an outer halved type has the advantage that no leg openings for passage of the user's legs need to be punched or only small-area leg openings need to be punched. That is, there is the advantage that when cut pieces (hereinafter also referred to as trims) are discarded, the material loss resulting from the trims (hereinafter also referred to as trim loss) can be suppressed.
However, any attempts to completely eliminate the trim loss would disable the formation of the edges of the leg openings along the peripheries of the groin region and the buttocks. Accordingly, taking the fit around the legs into consideration, even the outer halved type could not enable complete elimination of the trim loss.
As a solution of this problem, there has been proposed an underpants-type disposable diaper, wherein by configuring an outer body to be extensible to a crotch side, and extending (increasing the width of) a central portion of the outer body in a width direction to the crotch side relative to both sides thereof during manufacturing, edges of the leg openings in the outer body positioned in the lateral sides of the inner body obliquely face up to side edge portions, and the edges of the leg openings are formed along the peripheries of the groin region and the buttocks (Refer to Patent Documents 3 and 4).
In the related art, however, there still remains a problem that an extension step is needed during manufacturing.